The broad objectives of this research are: (1)\to elucidate the antigenic and structural relationship between nuclear and cytoplasmic poly(A) polymerases; (2)\to determine the structural relationship between polysomal poly(A)-binding protein(s) and poly(A) polymerase; (3)\to understand the role of poly(A) polymerase in gene expression; (4)\to explore the possibility that control of mRNA polyadenylation might occur via alteration in the amount of translatable mRNA for poly(A) polymerase; (5) to investigate the characteristics of a 3'\\\5' exonuclease associated with the most highly purified poly(A) polymerase; and (6) to begin cloning the gene for poly(A) polymerase. The specific aims of the proposal for the next year are to develop a satisfactory method for immunoprecipitating poly(A) polymerase. IgG purified by poly(A) polymerase affinity columns will be used for these studies. This then will be used in the in vitro translation experiments. The variations in the amount of translatable mRNA for poly(A) polymerase will be measured in liver and hepatomas and in response to steroid hormones. The mRNA will be enriched and cDNA cloning will be attempted. Finally, peptide mapping of poly(A) polymerase from the transplanted hepatoma, hepatoma induced by the azo dye 3' MDAB and polysomal binding proteins will be done.